The invention relates to new compositions of detergent additives for gasoline-type fuels and the compositions of fuels that contain them, alone or mixed with other detergent additives.
It is known that automobile engines have a tendency to form deposits on the surface of the engine elements, in particular on the carburetor orifices, the bodies of butterfly valves, fuel injectors, cylinder orifices and intake valves, because of oxidation and polymerization of various hydrocarbon-containing components of the fuel. These deposits, even when they are present only in small amounts, are often responsible for significant driving problems, such as the engine timing and poor acceleration. In addition, deposits in the engine can significantly increase the consumption of fuel and the production of pollutants. This is why the development of effective detergent additives for regulating these deposits assumes a considerable importance and was already the object of much research.
A new family of compounds that exhibit good effectiveness as additives that are intended to reduce the deposits in the injectors and in the intake valves has now been discovered.
The detergent additive compositions for gasoline-type fuels of the invention comprise at least one compound that corresponds to the following general formula (I): 
in which R1, R2, R3 and R4 each represent a hydrogen atom or a hydrocarbon radical, for example alkyl, with 1 to 30 carbon atoms, whereby at least one of R1, R2, R3 and R4 is a hydrocarbon radical; n is a number from 1 to 20, preferably from 1 to 10, m and mxe2x80x2 are each a number from 1 to 30, for example, from 1 to 20, preferably from 1 to 10, with m+mxe2x80x2 from 4 to 60, preferably from 5 to 30.
In the same formula, the concatenations: 
can respectively consist of patterns: 
that differ from one another by the nature of R1, R2, R3 and/or R4.
The compounds that are used in the invention generally come in the form of mixtures of compounds that differ from one another by the value of n, m and/or mxe2x80x2 and/or by the nature of radicals R1, R2, R3 and R4. Rather than compounds, it is then possible to speak of compositions.
The synthesis of the compounds or compositions defined above can be carried out as described below.
In a first stage, the polymerization of the tetrahydrofuran is carried out according to a known procedure and described, for example, in the work of P. Dreyfuss (Polytetrahydrofuran, Gordon and Beach Science Publishers, New York, 1982) in the presence of an acid catalyst, to obtain a polytetrahydrofuran of general formula (II):
HO"Brketopenst"CH2CH2CH2CH2O"Brketclosest"H
The polytetrahydrofurans that are being considered may have a mean molar mass of 200 to 3000.
The polytetrahydrofuran that is formed is then reacted with one or more compounds that have an epoxide function, of general formula (III): 
in which R1, R2, R3, and R4 represent a hydrogen atom or a hydrocarbon radical, for example alkyl, with 1 to 30 carbon atoms, whereby at least one of R1, R2, R3 and R4 is a hydrocarbon radical.
The conditions of the reaction are in general the following:
The polytetrahydrofuran is mixed with, for example, sodium hydride (at a rate of, for example, about 0.4% by weight). After having purged, under stirring, the reactor of the released hydrogen, the epoxide or an epoxide mixture is introduced in an amount that is calculated to obtain the desired value of m+mxe2x80x2, at a temperature of 80 to 180xc2x0 C., and the reaction mixture is kept at this temperature until the end of the consumption of the epoxide or epoxides. After returning to ambient temperature, the medium is diluted with an organic solvent, for example a hydrocarbon solvent, such as heptane, it is washed with water one or more times, then, after evaporation under reduced pressure of the organic phase, the desired product that corresponds to general formula (I) is obtained. 
In the invention, the detergent additive compositions as defined above can be added to gasoline-type fuels at concentrations of, for example, 20 to 5000 mg/liter. They can also be used mixed with any other detergent compound.